Milling cutters with detachable blades

ABSTRACT

Front milling cutter of the detachable blade type comprising blade inserts fitted in peripheral notches of a cutter body and secured by means of screws, characterized in that the bottoms of said notches consist of flat faces tangent to a cone coaxial with the milling cutter and converging in the forward direction thereof, so that the cutting edges of the blades are relatively close to each other.

O United States Patent 1151 3,673,655 Eydieux 1 July 4, 1972 541 MILLINGCUTTERS WITH 1,969,843 8/l934 Head ..29/10s x DETACHABLE BLADES2,001,021 5/1935 Heard ..29/105 x 2,586,428 2/1952 Hartman ..29/i05 [72]France R22,89l 6/1947 Head ..29/105 [73] Assignee: Regie Nationale desUsines Renault, Billancourt, France Primary Examiner-Harrison L. Hinson[22] Filed: May 18 1970 AttorneyStevens, Davis, Miller & Mosher pp38,361 57 ABSTRACT Front milling cutter of the detachable blade typecomprising [52] Cl blade inserts fitted in peripheral notches of acutter body and [51] secured by means of screws, characterized in thatthe bottoms [58] held of Search ..29/105, 105 A of said notches consistof flat faces tangent to a cone coaxial with the milling cutter andconverging in the forward direction [56] References Cited thereof, sothat the cutting edges of the blades are relatively UNITED STATESPATENTS close each Otherl,445,448 2/ l 923 Reisinger ..29/ I05 4 Claims,2 Drawing Figures MILLING CU'I'I'ERS WITH DETACHABLE BLADES Thisinvention relates in general to milling cutters and has specificreference to milling cutters of the insert or detachable blade type.

It is known that in the cutting of bevel, spiral and hypoid gears thereduction in the milling cutter diameter on the one hand and theincreased production rates of modem machines on the other hand are asource of difficult problems conceming the tool shape and fasteningmethod.

At present in milling cutterswith blade inserts theseare secured innotches having a bottom parallel to the axis of the milling cutter'body.The vertical positioning of the tooth is provided by a heel portiondisposed either in front of, or behind, the cutting face or edge of thetooth.

Due to their shape, these inserts are relatively expensive; in addition,the constant increment in the production rate of modern machines makesit compulsory to increase the number of blades in a same cutter, andwith the present trend of milling cutter design it is difficult to meetthese contradictory requirements without impairing the strength of theassembly.

An advantageous solution to these problems is brought by the presentinvention which provides a front milling cutter having blade insertsfitted in peripheral notches of the milling cutter body and securedtherein by means of screws, this cutter being characterized in that thebottoms of these notches are shaped to constitute flat faces tangent toa cone coaxial to the cutter and converging in a forward direction inrelation thereto, whereby the cutting edges of said blades arerelatively close to each other.

This design is attended by the following advantages:

a greater number of blades can be used for a given diameter;

the milling cutter constitutes nevertheless a rigid unit as in the caseof one-piece milling cutters;

an intermediate, shape-modifying blade can be positioned between theexternal and internal cutting areas for roughmilling gear wheels, afeature diflicult to achieve with onepiece milling cutters;

the blades are considerably cheaper and may be cut fromrectangular-sectioned stock bars easy to grind and stan dardize.

Moreover, by resorting to the tapered inclination to the notch bottomswhich corresponds to the external pressure angle of the blades, it ispossible to avoid the operation consisting in giving a predeterminedcontour to the corresponding blade face, thus reducing inasmuch theblade machining time.

Thus, the cost of these blades, constituting the wearing portion of themilling cutter, can be reduced considerably without appreciablyincreasing the cost of the cutter body and of its accessoriesconstituting the permanent or non-wearing portion of the tool.

An exemplary form of embodiment of the milling cutter according to thisinvention will now be described with reference to the attached drawingin which:

FIG. 1 is an axial section of the milling cutter according to thisinvention, and

FIG. 2 is a fragmentary front view of the cutter, wherein some notchesare shown without and the others with their inserts.

The milling cutter illustrated in the drawing comprises acylindro-conical cutter body 1 having formed at spaced intervals in itsouter periphery a plurality of notches 2 extending parallel to the axisof said body and having their bottoms constituted by flat faces tangentto a cone having the same axis as the cutter and converging towards thefront thereof, as shown only partially by the dash and dot line C.

The notches are positioned in close relationship on the front face ofthe milling cutter, so that for a given diameter at this position amaximum number of blades or insert tools can be fitted as clearlyapparent from FIG. 2.

In each notch 2 a blade 3 is secured by means of a screw 4 and preciseradial positioning of the blade 3 is obtained if necessary by providinga shim 5 also receiving the fastening screw 4 therethrou the axialpositioning being obtained by the engagement 0 tlus blade 3 against aroller 6 secured by means of another screw 7 engaging a tapped hole inthe rear portion of the notch bottom, all the rollers bearing against acommon ring 8 centered on, and secured by screws 9 to, the body 1 of themilling cutter. Thus, a plurality of sets of such rollers are providedin order to cover the desired adjustment range, and it may be noted thatthese rollers are extremely cheap considering the easy and fastadjustment of the blades which can be obtained therewith.

it will be noted that by using a tapered inclination of the notchbottoms, as illustrated, which corresponds to the external pressureangle 10 of the blades or inserts 3, the latter can be cut and groundfrom simple rectangular-sectioned bar stock, thus avoiding the necessityof giving a special contour to the corresponding outer face of theblade.

Under these conditions it may be estimated that the reduction in cost ofthe milling cutter which is ascribable to the present inventioncorresponds to about 40 percent in comparison with the cost of aheel-type blade, that the total cost of this milling cutter with a setof, say, twelve blades is reduced by 30 percent in comparison with thecost of a one-piece milling cutter having the same number of blades, andthat the useful life of the cutting tools for a same amount of wearexceeds by about 40 percent that of one-piece milling cutters having asame number of blades.

Of course, several modifications and variations may be brought to thespecific and single form of embodiment shown and illustrated hereinwithout departing from the basic principles of the invention as setforth in the attached claims.

What is claimed as new is:

1. A front milling cutter of the detachable blade type, comprising, acutter body having notches in the periphery of said body, blade insertsfitted into said notches and secured to said body by screws, eachnotched portion of said body having a bottom face which is flat andtangent to a cone coaxial with the milling cutter, said faces convergingtoward the front of said cutter so that the cutting edges of the bladesare closer to each other than their bases, each of said bottom faceslying in a plane which makes an angle with the axis of rotation of thecutter body which angle is substantially equal to the external pressureangle of the blades.

2. A front milling cutter according to claim 1, additionally comprisingrear abutment rollers secured by screws into the bottom face of thenotched portions of said cutter body, said rollers for axiallypositioning the blade inserts in said notched portions.

3. A front milling cutter according to claim 2, additionally comprisinga bearing ring which is common to all of said abutment rollers and iscoaxial with and secured to the cutter body.

4. A front milling cutter according to claim 1, additionally comprisingshims located between the blade inserts and the bottom faces of thenotched portions of said body, said shims adapted to receive fasteningscrews therethrough, and said shims for the radial adjustment of saidblade inserts.

* II i i l TED STATES ?A.TENT @FFECE QERTIFMIATE or to swim Pat 3673655Dated July 4, 1972 Inventor(s) Marius EYDIEUX It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Letters Patent will show the French priority No. 69/185630 of June 5,1969. (This was omitted from Letters Patent) Signed and sealed this 39thday of January 19-73.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GO'I'TSCHALK Attesting Officer Commissionerof Patents

1. A front milling cutter of the detachable blade type, comprising, acutter body having notches in the periphery of said body, blade insertsfitted into said notches and secured to said body by screws, eachnotched portion of said body having a bottom face which is flat andtangent to a cone coaxial with the milling cutter, said faces convergingtoward the front of said cutter so that the cutting edges of the bladesare closer to each other than their bases, each of said bottom faceslying in a plane which makes an angle with the axis of rotation of thecutter body which angle is substantially equal to the external pressureangle of the blades.
 2. A front milling cutter according to claim 1,additionally comprising rear abutment rollers secured by screws into thebottom face of the notched portions of said cutter body, said rollersfor axially positioning the blade inserts in said notched portions.
 3. Afront milling cutter according to claim 2, additionally comprising abearing ring which is common to all of said abutment rollers and iscoaxial with and secured to the cutter body.
 4. A front milling cutteraccording to claim 1, additionally comprising shims located between theblade inserts and the bottom faces of the notched portions of said body,said shims adapted to receive fastening screws therethrough, and saidsHims for the radial adjustment of said blade inserts.